Abstract: Magnetic tape reels, using file protect rings disposed within an annular channel concentric with the spindle opening within the tape reel, can be provided with a unique, access coding by defining a first plurality of recesses or projections on the bottom surface of the annular channel and a corresponding and mating second plurality of projections or recesses on the bottom and opposing surface of the file protect ring. The pattern of recesses, projections or both defined within the annular channel and on the bottom surface of the file protect ring uniquely associates each file protect ring with each tape reel such that a given ring will fit flushly with only one reel. A conventional electromechanical actuator senses whether or not the file protect ring is appropriately and flushly disposed within the channel, thereby preventing erasure or overwriting on the tape.